Cylindrical stencil with plastic end rings

ABSTRACT

An end ring for supporting a thin, perforate cylindrical printing member the end ring having printing member supporting and securing structure comprising integral electrical insulating plastic first, second, third, and fourth coaxial cylindrical portions. The first and third portions have a first outer diameter substantially equal to the inner diameter of the perforate member, the second portion has an outer diameter less than that first outer diameter and also has a roughened outer cylindrical surface, and the fourth portion has an outer diameter equal to the outer diameter of the perforate member. Also shown is a printing roll unit comprising a cylindrical perforate member secured, at each end, to such an end ring by an adhesive disposed on the roughened surface of the end ring&#39;&#39;s second portion.

United States Patent 1 Owren et al. Jan. 7, 1975 [54] CYLINDRICAL STENCIL WITH PLASTIC 1,955,077 5/1971 Germany 101/l28.l END RINGS 1,671,636 4/1970 Germany l0l/l27.l

[75] Inventors: Erling Owren, Foster; William McElroy, Cranston, both of R.l.

[73] Assignee: Cranston Print Works Company, Webster, Mass.

[22] Filed: Apr. 9, 1973 [21] Appl. No.: 348,979

[52] US. Cl 101/l27.1, 29/119, 29/123, 10l/l28.1,118/D1G.15 [51] Int. Cl B4ln 1/24 [58] Field of Search 101/1271, 128.1, 116; 29/110,1l9,1l8,l23;l18/D1G. 15

[56] References Cited UNITED STATES PATENTS 3,304,860 2/1967 Van Der Winden 10l/l28.l 3,556,004 1/1971 Mitter et a1 101/116 3,565,001 2/1971 3,599,565 8/1971 Feier et al 101/127.1X 3,608,482 9/1971 Bubley et al l0l/l27.1

FOREIGN PATENTS OR APPLlCATlONS 467,673 3/1969 Switzerland 101/1271 Primary Examiner-Edgar S. Burr Assistant ExaminerR. E. Suter [57] ABSTRACT An end ring for supporting a thin, perforate cylindrical printing member the end ring having printing member supporting and securing structure comprising integral electrical insulating plastic first, second, third, and fourth coaxial cylindrical portions. The first and third portions have a first outer diameter substantially equal to the inner diameter of the perforate member. the second portion has an outer diameter less than that first outer diameter and also has a roughened outer cylindrical surface, and the fourth portion has an outer diameter equal to the outer diameter of the perforate member, Also shown is a printing r011 unit comprising a cylindrical perforate member secured, at each end, to such an end ring by an adhesive disposed on the roughened surface of the end rings second portion.

10 Claims, 3 Drawing Figures Patented Jan. 7, 1975 FIG.- 2

FIG. 3

CYLINDRICAL STENCIL WITH PLASTIC END RINGS BACKGROUND OF THE INVENTION This invention relates to printing or coloring opera tions in which a cylindrical perforate printing member is employed, and, more particularly, to the support and reinforcement of such a cylindrical perforate printing member. Printing apparatus employing such printing members is discussed in Van Der Winden, U.S. Pat. No. 3,304,860.

In a typical construction a printing roll has heretofore comprised a nickel screen supported on aluminum end rings. The useful lifetime of rolls employing this construction has been limited by at least three problems: loosening of the end rings, damage to screens when printing Azoic colors, and damage to screens when printing cationic or basic colors.

SUMMARY OF INVENTION Principal objects of the present invention are the provision of improved support for such a printing member so as to simplify the manufacture, and prolong the useful lifetime, of a printing roll comprising such a member and the means of support.

According to the present invention, it has been discovered that the problems which developed with prior constructions are dependent to a previously unsuspected degree upon certain design parameters involving materials and dimensions. Thus, the loose end ring problem has typically involved separation of the end ring from the screen due to failure of the adhesive bond. The solution which reduced loose end rings to a minimum was use of an end ring formed from a plastic material. The improvement is apparently the result of increased bonding surface on the end ring, improved adhesion of the adhesive (e.g., Epoxy). to the plastic, and a true round end ring (as compared to offround" for the aluminum end rings). Also, increased surface area of the end ring where it engages the screen has been provided and has resulted in fewer damaged screens in the infrequent instances of end ring loosenmg. The problem of damaged screens in the printing of Azoic colors was resolved by the discovery of the existance of a galvanic cell involving the aluminum end ring as the anode, the nickel screen as the cathode, and the strongly alkaline printing paste as the electrolyte. In such a cell, the anode is subjectedto oxidation (corrosion) and the cathode to reduction. Hydrogen plates out on the cathode. While this is protective with most metals, in the case of nickel the hydrogenis absorbed into the nickel, the effect being referred to as Hydrogen Charging. We have found that nickel in this state is very brittle and that this has caused screen ruptures. The breaks in the screens have been found in the form of small slits b to 1 inch long running parallel to the screen circumference and within several inches from the end ring-and-screen joining. Very likely the embrittled area of the screen could not tolerate the flexing normally involved or responded to variations in torque action.

Again, according to the invention, the solution was found in a plastic end ring. Being non-conductive, the plastic end rings served to eliminate the cell by electrically isolating the nickel screen.

The problem of damaged screens in the printing of cationic or basic colors was also resolved by discovery of the existance of a galvanic cell involving the conventional aluminum end ring as the cathode, the nickel screen as the anode, and the acid printing paste as the electrolyte. The acids generally used include Acetic, Citric and Ammonium Sulfate. The action which takes place has been discovered to be a deplating of nickel from the screen. Measurements have been made of nickel screen thickness to show the thickness reduced from an original 0.003/0.0035 inch down to 0.00l/0.0()l5 inch. At the reduced thickness, the screen cannot support the torque action of printing or even its own weight and collapses.

The galvanic cell involved in the printing of cationics is the reverse of that in the case of Azoic colors. The development and use of plastic end rings solved this problem also by eliminating the cell in isolating the nickel screen electrically.

More specifically, according to the invention an end ring is provided for supporting a thin, perforate, cylindrical printing member. The end ring is made from an insulating plastic and comprises first, second, third, and fourth coaxial cylindrical portions. The first and third portions have a first outer diameter substantially equal to the inner diameter of the perforate member and the fourth portion has an outer diameter substantially equal to the outer diameter of the perforate member. The second cylindrical portion has an outer diameter less than the outer diameter of the first cylindrical portion and has a roughened outer cylindrical surface, thereby providing an appropriate surface for receiving an adhesive for bonding'of the perforate member to the end ring. In preferred embodiments the outer diameter of the second portion is approximately 0.020 inch less than the outer diameter of the first portion; each of the first and third portions has an axial length equal to at least one half the axial length of the second portion; and the first portion is greater in axial length than the second portion.

In another aspect of the invention a printing roll unit is provided which comprises a thin, perforate, metallic, open-end cylindrical member having a predetermined inner diameter anda predetermined outer diameter. The roll also comprises a pair of unitary insulating plastic end rings disposed respectively in the open-ends of the perforate member. Preferably, each ring comprises first, second, third, and fourth coaxial cylindrical portions having diameters and surfaces as described above. An adhesive is disposed on the roughened surface of the second portion and contacts the portion of the perforate member overlying that surface.

BRIEF DESCRIPTION OF THE DRAWING Other objects, features, and advantages of the invention will appear from the following description of a particular preferred embodiment with reference to the accompanying drawing, in which:

FIG. 1 is a side elevation of a printing roll unit constructed according to the present invention;

FIG. 2 is a sectional view through the axis of an end ring constructed according to the invention; and

FIG. 3 is an enlarged view of the perforate member supporting and securing portion of the end ring of FIG.

DESCRIPTION OF A PARTICULAR PREFERRED EMBODIMENT Referring to the drawing, a printing roll unit 10 comprises a thin, cylindrical, metallic (e.g., nickel), perforate member 12 with end rings 14 disposed within each of the open-ends of the member 12. The unit 10 is supported in a printing apparatus in a conventional fashion for rotation and a conventional system for supplying printing fluid to the interior of the screen is also provided. Often the member 12 is simply a screen having portions of its surface open to the flow of printing fluid from the interior to the exterior of the screen and portions masked. Occasionally the member 12 may be a delicate, thin walled cylindrical member rather-than a true screen. Its use in the printing apparatus is the same, however, as are the problems of supporting and securing such a delicate perforate member. It will be understood that the support problems for cylindrical members of the type described above is substantially different from the problems attendant use of the more rugged, thick metal cylinders in some printing roll units as a uniform underlayer for the actual screen. The support of these heavier cylindrical members is simplified by their inherent rigidity and the greater mass of material providing, for example,, an adequate thickness such that the cylinder may be secured to an end ring with a series of screws disposed around the circumference.

Referring again to the drawing,'each end ring 14 is made from polyterephthalate and comprises a supporting and securing portion 16 which is inserted into the open-end of the perforate member 12. The end ring 14 also includes a portion 18 for engagement,'in a conven tional fashion, with the apparatus which actually rotates the unit 10, as well as a transition portion 20 between portions 16 and 18. The end ring 14 is rotationally symmetrical, with the portions 16, 18, 20 having a common axis 22 (see FIG. 2).

The portion 16 itself comprises first, second, third, and fourth coaxial portions 24, 26, 28 and 30 respectively. The portions 24 and 28 act as supports for the perforate memberl2 and thus have an outer diameter substantially equal to the inner diameter of the member 12 (e.g.,'in one particular preferred embodiment, approximately 8 inches). The surface 32 of portion 30 is raised above the surface 34 of portion 28 by a distance approximately equal to the thickness of the member 12, to provide a smooth outer surface for the unite 10 as a whole. The exposed shoulder 36 between surfaces 32 and 34-also acts as a stop for the edge of the perforate member 12. With a typical thickness of the member 12 of 0.003 to 0.0035 inch, the outer diameter of portion 30 would thus be approximately 0.007 inch greater than the outer diameter of portions 24 and 28.

The portion 26 is of reduced diameter, having its surface 38 approximately 0.010 inch below surface 34. Portion 26 thus has an outer diameterwhich is approximately 0.020 inch less than the outer diameter of portions 24 and 28. Additionally, the surface 38 is roughened compared to the remaining surfaces of the molded plastic end ring 14. This is indicated in FIG. 1 by the shading of surface 38.

As best seen in FIG. 3, portions 24 and 28 have an axial length preferably at least half as long as the portion 26, the portion 24 is actually of greater axial length than portion 26.

As seen in FIG. 1, an adhesive 40 is disposed on the surface 38 having sufficient mass to fill the shallow depression of portion 26 and contact the'overlying portion of the perforate member 12 to secure the perforate member to the end ring 14. A suitable adhesive is Scotchweld 1751A or 1751B available from 3-M Company.

In operation, it will be seen that the delicate perforate member 12 will be supported by portions 24 and 28 on each side'of the screen segment which is bonded to the end ring '14 (i.e., that portion of the screen overlying surface 38). The substantial axial length of the support portions 24 and 28, and especially the extensive length of portion 24, prevent stresses within the delicate member 12 from causing a buckling" or bending of the member 12 in the region above surface 38 during or after the setting of the adhesive. The roughening of surface 38, furthermore, provides for an increased strength of the bond between the adhesive and the member 14. The shoulder 36, at the interface of portions 28 and 30, causes the end rings 14 and the member 12 to act as a unit in relation to any axial forces. The above-described relationship between portions 28 and 30, therefore, prevents substantially all axial forces from being transmitted from end ring to screen (or vice versa) through theadhesive 40 and thus by preventing shearing forces from acting on the hand between adhesive 40 and delicate perforate'member 12 provides for a prolonged lifetimeof the bond produced I by the adhesive.

Furthermore, the provision of unitary end rings formed from plastic in general, and polyterephthalate in particular, has itself increased the useful lifetime of printing roll units.

While a particular embodiment has been described in detail, other embodiments will be seen to be within the scope of the invention and the appended claims.

We claim:

1. An end ring for supporting a thin, perforate cylindrical printing member the end ring having printing member supporting and securing structure comprising integral electrically insulating plastic first, second, third, and fourth coaxial cylindrical portions, said first and third portions having a first outer diameter substantially equal to the inner diameter of said perforate member, said second portion having an outer diameter less than said first outer diameter and also having a roughened outer cylindrical surface, and said fourth portion having an outer diameter equal to the outer diameter of said perforate member.

2. An end ring as claimed in claim 1 wherein said outer diameter of said second portion is approximately 0.0020 inch less than said first outer diameter.

3. An end ring as claimed in claim 2 wherein said first outer diameter is approximately eight inches.

4. An end ring as claimed in claim 1 wherein said outer diameter of said fourth portion is approximately 0.007 inch greater than said first outer diameter.

5. An end ring as claimed in claim 1 wherein each of said first and third portions has an axial length equal to at least one half the axial length of said second portion.

6. An end ring as claimed in claim 5 wherein the axial length of said first portion is greater than the axial length of said second portion.

7. A printing roll unit comprising:

a thin, perforate, open-end cylindrical member having a predetermined inner diameter and a predetermined outer diameter;

a pair of unitary electrically insulating plastic end rings disposed respectively in the open ends of the perforated member;

said cylindrical member being secured to each end ring by an adhesive;

wherein each end ring comprises first, second, third and fourth coaxial cylindrical portions, said first and third portions having outer surfaces in contact with the inner surface of said perforate member, said second portion having an outer diameter less than said perforate member inner diameter and having its outer surface roughened, and said fourth portion having an outer diameter equal to said perforate member outer diameter; said adhesive disposed on said roughened outer surface of said second portion and contacting the portion of said perforate member overlying that surface.

8. A printing roll unit as claimed in claim 7 wherein each of said first and third portions has an axial length equal to at least one half the axial length of said second portion.

9. A printing roll unit as claimed in claim 8 wherein the axial length of said first portion is greater than the axial length of said second portion.

10. A printing roll unit as claimed in claim 7 wherein each end ring is formed from polyterephthalate. 

1. An end ring for supporting a thin, perforate cylindrical printing member the end ring having printing member supporting and securing structure comprising integral electrically insulating plastic first, second, third, and fourth coaxial cylindrical portions, said first and third portions having a first outer diameter substantially equal to the inner diameter of said perforate member, said second portion having an outer diameter less than said first outer diameter and also having a roughened outer cylindrical surface, and said fourth portion having an outer diameter equal to the outer diameter of said perforate member.
 2. An end ring as claimed in claim 1 wherein said outer diameter of said second portion is approximately 0.0020 inch less than said first outer diameter.
 3. An end ring as claimed in claim 2 wherein said first outer diameter is approximately eight inches.
 4. An end ring as claimed in claim 1 wherein said outer diameter of said fourth portion is approximately 0.007 inch greater than said first outer diameter.
 5. An end ring as claimed in claim 1 wherein each of said first and third portions has an axial length equal to at least one half the axial length of said second portion.
 6. An end ring as claimed in claim 5 wherein the axial length of said first portion is greater than the axial length of said second portion.
 7. A printing roll unit comprising: a thin, perforate, open-end cylindrical member having a predetermined inner diameter and a predetermined outer diameter; a pair of unitary electrically insulating plastic end rings disposed respectively in the open ends of the perforated member; said cylindrical member being secured to each end ring by an adhesive; wherein each end ring comprises first, second, third and fourth coaxial cylindrical portions, said first and third portions having outer surfaces in contact with the inner surface of said perforate member, said second portion having an outer diameter less than said perforate member inner diameter and having its outer surface roughened, and said fourth portion having an outer diameter equal to said perforate member outer diameter; said adhesive disposed on said roughened outer surface of said second portion and contacting the portion of said perforate member overlying that surface.
 8. A printing roll unit as claimed in claim 7 wherein each of said first and third portions has an axial length equal to at least one half the axial length of said second portion.
 9. A printing roll unit as claimed in claim 8 wherein the axial length of said first portion is greater than the axial Length of said second portion.
 10. A printing roll unit as claimed in claim 7 wherein each end ring is formed from polyterephthalate. 